(a) Field of the Invention
The present invention relates to a liquid crystal display, a driving method thereof and a frame memory for use in the liquid crystal display.
(b) Description of the Related Art
In recent years, lightness and slimness of personal computers and television sets requires light-weighted and thin displays. According to such a requirement, flat panel displays (“FPDs”) such as liquid crystal displays (“LCDs”) has been developed in replacement of cathode ray tubes (“CRTs”).
The LCD, which includes two panels and a liquid crystal layer with dielectric anisotropy disposed therebetween, displays desired images by applying electric field to the liquid crystal layer and adjusting the strength of the electric field to control the amount of light passing through the panels. Such LCDs are representatives of FPDs, and among the LCDs, a TFT LCD using thin film transistor (“TFTs”) as switching elements is mainly employed.
In addition, since the TFT LCD is used not only as a display of computer but also as a display of television, implementation of moving pictures is increasingly required. The human recognizes as moving pictures subsequent pictures displayed at high speed equal to or larger than 24 frames per second. This is due to an afterimage effect that human eyes remember recognized pictures for 0.04 seconds.
An impulsive luminescent type display such as a CRT has a blank interval between previous and next frames, which is compensated by the afterimage effect. Therefore, the larger difference in brightness between before and after frames cannot prevent the implementation of natural moving pictures due to the blank interval. However, a conventional TFT LCD has a drawback that it is not easy to implement moving pictures because of slow response time. To improve this problem of response time, a conventional art has employed a TFT LCD in an optically compensated band (“OCB”) mode or using a ferroelectric liquid crystal (“FLC”) material.
However, an OCB mode LCD or an FLCD has a panel structure different from a normal TFT LCD. The applicant solved the above problem by adding a gray signal modifier capable of generating modified data voltages without changing a panel structure of the TFT LCD, in the Korean Patent Laid-Open Number 2001-0077568 entitled “A Liquid Crystal Display and Driving Method Thereof” (filed on Feb. 3, 2000 and laid-open on Aug. 20, 2001).
A frame memory for the gray signal modifier for storing and outputting the gray signal may be embedded in the gray signal modifier, however, it is preferable in view of price to be implemented as an external memory shown in FIG. 3.
In this case, the gray signal modifier needs pins for interfacing the external frame memory. However, the size of die of the gray signal modifier is increased proportional to a square of the total number of the pins, and this in turn increases production cost.